Electric motor control system



June 1, 1943. A. L. HoLcoMB ELECTRIC MOTOR CONTROL SYSTEMS Filed March15, 1940 9 Sheets-Sheet l /NVENT'OR L. HOLCOMB By Wlludi June 1, 1943.A. L.. HoLcoMB 2,320,434

ELECTRIC MOTOR CONTROL SYSTEMS Filed March l5, 1940 9 Sheets-Sheet 2ATTQRNFV June 1, 1943. A. L. HoLcoMB ELECTRIC MOTOR CONTROL SYSTEMS A9Sheets-Sheet 3 Filed March 15, 1940 /N VEA/Tof? l A. L. HOL COMB y @,Mdr

June 1, 1943. A. L. HoLcoMB 2,320,434

ELECTRIC MOTOR CONTROL SYSTEMS Filed March 13, 1940 9 Sheets-Sheet 4RECORDER POWER SUP/L Y S /NvE/v TOR ALHOLCOMB A T TORNE V June 1, 1943.A. L. HoLcoMB ELECTRIC MOTOR CONTROL SYSTEMS Filed March 13, 1940 49Sheets-Sheet 5 /NVENTOR A. L. HOL COMB A 7' TORNE Y June l, 1943. A. l..HoLcoMB 2,320,434

ELECTRIC MOTOR CONTROL SYSTEMS Filed March 15, 1940 9 sheets-sheet e/NvE/v Ton A. .HOL COMB @y @wat ATTORNEY June 1, 1943. A. L. HoLcoMBELECTRIC MOTOR CONTROL SYSTEMS Filed March 13, 1940 9 Sheets-Sheet '7O09 O l RN v S .0?. EN

/NVENTOR BVA. [..HOLCOMB ATTORNEY June 1, 1943.

A. L.. HoLcOMB ELECTRIC MOTOR CONTROL SYSTEMS 9 Sheets-Sheet 8 FiledMarch 13, 1940 INVENTOR AL. HOL C 0MB ATTORNEY June 1, 1943.

A. L. HOLCOMB ELECTRIC MOTOR CONTROL SYSTEMS Filed March l5, 1940 9Sheets-Sheet 9 vd. @Fi

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ATTORNEY Patented June l, 1943 UNITED STATES PATENT OFFICE ELECTRICMOTOR CONTROL SYSTlli/I Application March 13, 1940, Serial No. 323,674

19 Claims.

This invention relates to motion picture and sound recording systems andparticularly to systems for controlling the motors and other apparatusused in such systems.

The object of the invention is a complete system of control adapted forvarious types of power supply and for the various conditions experiencedin the motion picture studios and on location.

A feature of the invention is a cabinet for controlling a plurality ofmotion picture cameras and, if desired, one or more sound re corders.The control cabinet may be used individually or in combination withother cabinets.

Another feature of the invention is the provision of means for startingeach motor ndividually at the camera, for starting one or all of themotors associated with a given cabinet at the cabinet and for startingany or all of the motors associated with all the cabinets in a system atany desired cabinet.

Another feature of the invention is the provision oi means for bloopingor simultaneously making a starting mark on the picture and the soundrecord of all the cameras and recorders associated with a cabinet or aplurality of cabinets. All the cameras and recorders in the whole systemmay be simultaneously blooped from any cabinet in the system. Preferablythe marking agency will take the form of an alternating current suppliedto a lamp or other device in the camera or sound recorder or analternating current supplied to the recording device itself.

A further feature of the invention is the pro vision of running andsynchronism indicators at each cabinet to show when the motorsassociated in the system are running at full speed and to indicate whena motor is out of synchronism.

Other features of the invention are an auxiliary cabinet for extendingthe control facilities of a cabinet to a distance, means for controllinga recorder permanently installed in the studio, and an auxiliary cabinetfor controlling motors located at an abnormal distance from the powersupply.

Still other features of the invention will be apparent from thefollowing description and the drawings and the scope of the invention isnot in any way limited to the features mentioned above, but only as setforth in the claims.

In the drawings,

Fig. 1 diagrammatically shows the invention embodied in a systemoperating onv either alternating or direct current.

Fig. 2 diagrammatically shows the invention current.

Fig. 3 diagrammatically shows the invention embodied in a systemoperating on direct current.

Fig. 4 schematically shows the connections of a motor.

Figs. 5 and 5--A schematically show the wiring of an alternating anddirect current control cabinet.

Figs. 6 and 6-A schematically show the wiring of an alternating currentcontrol cabinet.

Fig. 7 schematically shows the wiring of a cabinet for controlling astudio recorder.

Fig. 8 schematically shows the Wiring of a cabinet for extending thecontrol apparatus of an alternating current cabinet to a distance.

Figs. 9 and 9-A schematically show the wiring of a direct currentcontrol cabinet.

Fig. l0 schematically shows the wiring of an auxiliary cabinet forcontrolling a motor located at a distance from the control cabinet.

Following the introduction of sound record- L ing synchronized withmotion pictures, many studio practices and techniques were developed toefliciently utilize this new medium. After this decade of development,these practices have become better defined and the requirements of acontrol system for practicing these techniques may now be determined.Based upon information from a number of the largest studios out liningthe facilities which the studios consider to be desirable, the presentinvention was conceived in order to provide these facilities in a cheapand convenient form.

All of the motors of the cameras lming a given scene must run insynchronism, thus an electrical interlock is provided between the cameramotors. The motor of the sound recorder must run at a standard and veryconstant speed. When the motors of the picture cameras are running atnormal speed, the motor of the sound recorder may be electricallyinterlocked with the motors of the cameras.

In the majority of the studios as a general rule, commercial three-phasealternating current is available. Thus the motors of the cameras andportable recorders in the present system are adapted to operate assynchronous motors on three-phase alternating current. However, in manycases, particularly on location, no alternating current power isavailable and the system must be operated on direct current. The motorsof the present system are therefore adapted to operate also on directcurrent with a three-phase alternating current interlock circuit betweenthe various motors.

The armatures are Wound with a distributed winding, commonly found indirect current machines, connected to a commutator. The armature windingis also tapped at three electrically equidistant points which are ledout through slip rings. The eld has the usual direct current shunt andseries windings, so arranged as to produce well defined salient poles. Ashort-circuited damper winding is also placed in recesses in the polefaces. When operating on direct current, the power is supplied in theusual manner to the commutator, and the field windings, and the tappingsfrom the armature windings are in'- terconnected with the similartappings of the other motors. If any moto-r should drop out ofsynchronism with the other motors, a considerable interchange of currentwill take piace between motors through the interconnected armaturetappings. When operating on alternating current, three-phase alternatingcurrent is supplied to the tappings of the armature winding, and thecurrent in the armature reacts with the damper winding to start themotor like an induction motor. The eld windings, in this case, areexcited by current from the commutator. At full speed the motor runs asa synchronous motor, but, due to the direct current excitation of thesalient poles, the interlock to the supply line is more rigid than thatobtained from the variable reluctance synchronous motors commonly usedfor this purpose. If a motor is running in synchronism with the supplyline and drops out oi synchronism, a reversal of polarity at thecornmutator brushes takes place each time the motor slips back a pole.This change in polarity reverses the polarity of the elds and this eiectaids the armature to pull into synchronisin when starting.

As indicated in Fig. l the switches and other control devices associatedwith each motor are wired to a jack and the motor itself is wired to aplug. These jacks and plugs may be in the form of receptacles mounted ina small cabinet attached to the machine or they may be attached to theend of suitable cords. Similarly, the corresponding jacks and plugs inthe control box may preferably be in the form of receptacles mounted inthe box or may be attached to suitable cords. If the jacks and plugs arein the form of receptacles mounted on the motors and in the controlcabinets, then cords suitably terminated at each end in a jack or plugmay be provided for interconnection. The plug of the control cabinetcarrying the signal and control wires is plugged into the control jackof the corresponding motor and the power plug of the motor is pluggedinto the corresponding jack on the control cabinet. When the system isadapted for operation on either alternating current or direct current,two power jacks, one for alternating current and the other for directcurrent are provided in the control cabinet for each motor. The powerplug of the motor is plugged into the jack corresponding to the type ofpower to be used and this type of power is also supplied Yto a jacks areprovided in the control cabinet to sup- 7`5 ply power to the motor ofthe sound recorder and to control the operation of the recorder.

The sytsern shown in Fig. l is adapted for operation on eitheralternating current or direct current. However, as a large proportion ofthe usual motion picture production is produced in large studios wherecommercial power is available, in lsuch cases the control cabinet may besimpliiied by omitting the direct current facilities and providingfacilities only for alternating current. Also, in many of the studios,the sound recorders are permanently installed in a suitable room and aredirectly supplied with alternating current for the motor of the soundrecorder. In such cases, as shown in Fig. 2, the circuits of the controlcabinet may be arranged to control the motor of an eXtra camera in piaceof a portable recorder and may be supplied with power from the recordingroom. rThe motor of the sound recorder may still be controlled at thecontrol cabinet through the recorder control circuit and the motors ofthe cameras associated with the control cabinet may be controlled at therecorder through the recorder control circuit. An alternating currentcontrol cabinet of this type, supplied with power from the recorderroom, may be associated lwith an alternating current control cabinetindependently supplied with power. Either of these types or alternatingcurrent control cabinets may be associated with the dual alternatingcurrent, direct current cabinet shown in Fig. l, when this dual cabinetis operating on alternating current. Any or all of the alternatingcurrent control cabinets may also be controlled from a distance throughan extension control cabinet, which enables a supervisor on the motionpicture set to control the starting of all the motors and the marking ofall the lms.

If a large amount of recording is to be done on location wherealternatingcurrent power is not available, the dual alternating current,direct current cabinet shown in Fig. 1 may be simplied by the omissionof the alternating current facilities to make a direct current controlcabinet as shown in Fig. 3. A plurality of these direct current controlcabinets may be associated together and they may be associated with oneor more of the dual alternating current, direct current control cabinetswhen such cabinets are operated on direct current. As portable soundrecorders are generally used on location, these may be supplied withpower from the control cabinet. Ii a camera is located so far away fromthe control cabinet that the resistance of the leads to the motor causesunsteady operation of the motor, an extension box having a localsupplyoi power may be provided for such motors.

As indicated on Fig. l, the motor supply and control circuit shown onFig. 4 is associated with the alternating current, direct currentcontrol cabinet shown in Figs. 5 and 5-A and these Iigures of thedrawing should be considered together.

While the alternating current, direct current control cabinet shown inFigs. 5 and 5-V-A is arranged to control the motors of three. camerasand one recorder, the circuit is not necessarilyV limited to such anarrangement and may easily be Inodied to control a large number ofcameras or recorders or both. However, for the average motion picturescene, experience Vhas shown that three cameras and one recorder areusually sufficient and if a more elaborate equipment should be required,it is usually preferable to use `more than one control cabinet as shownin Fig. 1.

In Fig. 5 the control circuit for the motor of camera No. 3 is shown infull and the similar circuits for cameras Nos. 1 and 2 need not be shownas these circuits are essentially duplicates of the circuits shown forcamera No. 3. A control plug and two power supply jacks, one for directcurrent and one for alternating current, are supplied for each oi' themotors of the three cameras and the motor of the recorder and arerespectively numbered from I to 4. The jack and plug numbered 5 in Fig,5-A are provided for interconnecting two cabinets. The two power supplyplugs numbered 6 are respectively provided for the direct current andalternating current power supply.

A storage battery, or other convenient supply of direct current, may beconnected to the upper or direct current part of the plug P6, Fig. 5-A.

The positive terminal of the current supply is connected to the upperterminal of the plug P6 and the negative terminal oi the power supply tothe lower terminal of the plug P6. The power supply or battery mayconveniently be tapped and intermediate potentials supplied to theintermediate terminals of the plug P6. In one typical embodiment of theinvention a 96-volt battery was used and was tapped at 84, 72, 60 and 48volts. The positive terminal of the power supply and the intermediatetaps are connected from the terminals of the plug P6 direct to thecontacts of the voltage control switch II, A voltmeter I2 may beconnected from the contact arm of the switch I I to the negative batterylead I4 to indicate the voltage selected by the switch II and suppliedto the motor. By this adjustment of the voltage supply, the motors ofthe cameras and recorder may be run at less than normal speed, ifdesired, for special eii'ects. The contact arm of switch l I isconnected to a positive bus-bar I3 which is wired through the controlcircuit of all of the motors. The negative terminal of the power supplyis connected through the lower terminal of the upper part of the plug P6to the negative bus-bar I4 which is also wired through the controlcircuit of all the motors and is further connected up the left side ofthe drawings to the second terminal of the control plugs PI to P4,respectively, associated with the camera and recorder motors.

Disconnect switches, such as the switches I5, I6, are provided for eachmotor so that any motor not in use may be disconnected from the cabinet.Normally the disconnect switches l5, I 6 of all the motors in use areclosed.

A circuit may be traced from the negative busbar I4 through the secondterminal of plug P3, Fig. 5, to the second terminal of the jack 25, Fig.4, through the film buckle switch 26 and the switch l1, when operated bythe camera man, to the fourth terminal of the jack 25, thence to thefourth terminal of plug P3, Fig. 5, wire I8, lefthand break contact ofrelay I9, wire 20, contact of switch I5, wire 2I, winding of relay 22,busbar 23, Figs. 5 and 5--A, to the upper or full voltage terminal ofthe upper section of plug P6, thence through the power supply or batteryto the negative bus-bar I4. The iilm buckle switch 26, Fig. 4, isnormally closed and is opened by the film in the camera only when thefilm buckles and becomes jammed in the mechanism. Thus when the cameraman closes the switch I1 of Fig. 4, mounted on the camera motor, relay22 will be operated, A circuit may also be traced from the negativebus-bar I4 through the camera switch I 1, wire I8, contacts of relay I9, wire 20, contacts of switch I6, wire 24, winding of relay 21 to thepositive bus-bar 23, thence through the battery. When the camera mancloses switch I1 in Fig. 4, relay 21 will be operated over this circuit.

The operation of relay 22 closes a circuit from the negative bus-bar I4through the right-hand make contact of relay 22, resistor 23, wire 29 tothe lower terminal of the upper part of the jack J3 and thence to thelower terminal of plug 30, Fig. 4, through the series field 3l andarmature 32 of the camera motor to the fifth terminal of plug 30, thenceto the fifth terminal of the upper part of jack J3, wire 33, resistor34, left-hand make contact of relay 22, bus-bar I3, contact arm ofswitch II, Fig. 5-A, to a selected tap on the power supply and throughthe power supply back to the negative bus-bar I4. This circuit willsupply power at a controlled voltage to the series iield and armature ofthe motor. In Fig. 5A the full Voltage terminal of the power supply isconnected to the upper terminal of the upper section of the plug P6,thence through wires 23 across the drawing to the right-hand contact ofswitch II, thence upward to Fig. 5 through the field rheostat 35 and, ifdesired, the added resistor 36, wire 31 to the fourth terminal of theupper section of jack J3, thence to the fourth terminal of the plug 3,Fig. 4, through the motor shunt eld 38 and the series field 3l to thelower terminal of the plug 36, thence to the lower terminal of the uppersection o1" the jack J3, Fig. 5, wire 29, resistor 28, right-hand makecontacts of relay 22, to the negative bus-bar I4, thus supplying currentto the shunt ield or" the motor. The camera motor, Fig. 4, thus may bestarted when the switch I1 is closed.

In many studios, before a take is lmed, the take number, scene number,production and other information is written on a siate, the camera motoris started and the slate is photographed on the rst few frames of thefilm. The switch I1 is provided so that each camera man may r slate hiscamera as soon as he is ready to photograph the scene.

The resistors 28, 34, Fig. 5, reduce the voltage supplied to the motorat the start so that light loads will not be started too abruptly. Dueto the heavy current drawn by the motor during starting and theconsequent loss of voltage in the resistors 28 and 34, the relay 39 willnot be operated. However, when the motor has attained suicient speed,the back electromotive force generated by the armature will reduce thecurrent flowing in the motor, thus reducing the voltage loss in theresistors 28 and 34 until sufcient Voltage appears to operate relay 39which will then short-circuit the resistors 28, 34 and connect themotors directly to the supply bus-bars.

In interlooked motors of this type, in addition to the usual connectionsbetween the armature winding and the commutator, the armature winding isalso tapped at three electrically equidistant points. As shown in Fig.4, these tappings are wired to the three upper terminals of the plug 30and are connected through the cord to the three upper terminals of theupper section of the jack J3, Fig. 5. The upper terminal oi' the jack J3connects through wire 40, lamp 4I,

' wires 42 and 43, left-hand make spring of relay 21, wire 44, to theinterlock bus-bar 45, The second terminal of the jack J3 connectsthrough wire 46, lamp 41, wire 48, center make terminals of relay 21,wire 49, to the interlock busbar 50.

The third terminal of the jack J3 connects through wire 5|, lamp 52,wire 53, right-hand make terminals of relay 21, wire 54, to theinterlock bus-bar 55. As the motors of cameras I and 2 are wiredsimilarly to the wiring of the motor of camera 3, the operation of therelays, such as relay 21, will connect the armature tappings of all themotors to the common interlock bus-bars 45, 50, 55 through the ballastlamps such as 4I, 41 and 52.

The lamps 4|, 41, 52 in the connection from each armature tapping to theinterlock bus-bar, may be ordinary coil lament incandescent lamps ofsuitable carrying capacity. For slight differences in phase between amotor and the interlock bus-bar, the synchronizing currents are small,the resistances of the filaments of the lamps will be only a littlegreater than the cold resistance of the lament, thus the motors willquickly pull into synchronism without hunting. For large differences inphase between a motor and the synchronizing bus-bars, the synchronizingcurrents may become rather large and would tend to burn the motorcommutators, but this large current causes the resistances of thefilaments of the lamps 4I, 41 and 52 to increase to a value approachingthe hot resistance of the iilament and this added resistance will limitthe interlock current to a safe value. The lamps 4|, 41, 52 will alsoindicate the phase relationship of the motor because when the fieldrheostats of the individual motors are properly adjusted to operate eachmotor at the same speed, little current is interchanged through thelamps and the filaments remain cold. If a motor is in step but tendingto pull out, the lamps will show a steady glow which increases inbrightness to the point at which the motor breaks out of synchronism,indicated by a bright iickering of the lamps.

The sound recorder is equipped with a motor which may be of the samegeneral type as the camera motor and may have an individual startingswitch connected as shown in Fig. 4. The control wires from the motor-driving the sound recorder are connected to plug P4, Fig. 5--A andthepower wires are connected to the upper section of jack J4. The controlapparatus associated with the motor on the sound recorder 1ssubstantially the same as the control apparatus associated with thecamera motor and operates in substantially the same manner. Thedisconnect switches 55, A51 correspond to the disconnect switches |5,I6, in Fig. 5, the start relay 58 corresponds to the start relay 22, theslow start relay 59 corresponds to the slow start relay 39, theinterlock switching relay 60 corresponds to the interlock switchingrelay 21 and the eld rheostat 6I and resistor 62 correspond to the fieldrheostat and resistor 36. When the switch at the sound recorder motor isclosed, this motor will start in substantially the same manner asdescribed hereinabove in relation to the camera motor. As the soundrecorder ymust run at a very steady and constant speed, the tappngs fromthe armature winding are connected directly to the interlock bus-bar,the ballast lamps corresponding to 4I, 41, 52 being omitted. The motoron the sound recorder will thus tend to run at a very constant speed andwill also tend to make the camera motors synchronize with it.

In many cases, there is an advantage in being able to start all themotors associated with a certain production simultaneously from onecontrol cabinet. A circuit may be traced from thenegative batterybus-bar and the plug P6, Fig. 5-A, through wire 63, resistor 64, lowermake spring of switch 65, wire 66, through the winding of relay I9, Fig.5, wire 51, upper make springs of switch (i5, Fig. 5-A, to the positivebattery bus-bar 23. The operation of switch will thus cause theoperation of relay I9, Fig. 5. When relay I9 operates, a circuit isclosed from negative battery bus-bar I4 through the second terminal ofplug P3, Fig. 5, to the second terminal of jack 25, Fig. 4, through thelm buckle switch 26 to the third terminal of jack 25, thence to thethird terminal of the plug P3, Fig. 5, wire 58, to the left-hand makecontact of relay I9, wire 20, switches I5 and I6, the windings of relays22 and 21, to the positive battery bus-bar 23. A circuit may also betraced from ythe negative battery bus-bar I4 through the second terminalof the plug P4, Fig. 5-A. to the second terminal of the jack 25, Fig. 4,to the third terminal of jack 25 to the third terrninal of plug P4, Fig.E-A, wire 11, right-hand make contact of relay I9, Fig. 5, wire 18,switches 56 and 51, windings of relays 58 and 60 to the positive batterybus-bar 23. Thus by closing switch G5 and operating relay I9, the motorsassociated with camera No. 3 and the sound recorder will start, eventhough the individual switches at the motors are not operated. A relay,similar to relay I9, may be provided for the other two camera motors sothat all the motors associated with the control cabinet may be startedby the operation of the switch 65. If desired, separate switches may beprovided to control the starting of each two motors.

A circuit may be traced from the positive battery bus-bar 23 on theright-hand side of Fig. 5 through lamp 69, resistor 10, wire 1|, wire29, resistor 28, right-hand make contact of relay 22, to the negativebattery bus-bar I4. Thus, whenever relay 22 is operated to start themotor of camera No. 8, the lamp 69 is lighted and indicates at thecabinet that the motor is running. This indication is desirable when themotor has been started by the camera man for slating or othernonsynchronous operation, as it permits the operator at. the cabinet toadjust the field rheostat to give the correct motor speed as shown onthe tachometer while the motor is running, thus avoiding starting themotor only for this purpose. A lamp of this character may be providedfor each motor associated in the system, including the recorder' motor.f

When the system is to be operated on alternating current, three-phasealternating current from some convenient supply is connected to theupper three terminals of the lower section of plug P6, Fig. 5-A. In atypical embodiment of the inventicn, the motors were wound to operate on96- volt direct current, thus the three-phase supply was,v about 65voltsso that the voltages in the interlock circuit would be about the same inboth cases. In such a case, the power of the motor on alternatingcurrent, will be somewhat less than the power onr direct current, butallowance for this dillerence may be made in the design of the motor.Normally the motors are Vmade. large enough to operate satisfactorily onalternating current and when operated on direct current, the motors havea slight surplus of power over the requirement.

The three-phase power supply is connected to the upper three terminalsof the lower section of the plug P6, Figs. 5-A, and thus ls connecteddirectly to the interlock bus-bars 45, 50 and 55. When the powersupplyis plugged into the plug .circuit the resistors 8i) and 82.

P6, the switch 14 is operated. The low voltage tappings of thethree-phase autotransformer 15 are permanently connected to thethree-phase bus-bars 45, 50 and 55. The upper make spring of switch 14closes a circuit from the center autotransformer to the bridge-connectedrectifying network 19. This rectifier network supplies current to thevarious control lamps, relays, etc., in place ofv the current which,when operating on direct current, is supplied by the power battery. Whenthe system is operated on alternating current, the disconnect switches,such as I8 and 51. for .all'of the motors are closed, and the directcurrent disconnect switches, such as I5 and 58 are opened. A circuit maybe traced from the left-hand, or negative, terminal of the rectiiying4network 16, wire 53, negative bus-bar I4, second terminal of plug P3,Fig. 5, second terminal of jack 25, Fig. 4, through switch and switch i1when operated by the camera man, lfourth terminal of jack 25, Fig. 4,and of plug P3, Fig. 5, wire I 8, left-hand break springs of relay I9,lower make springs of switch I6, wire 24, winding oi relay 21, positivebus-bar 23, to the right-hand or positive terminal of the rectifyingnetwork 16. Thus, when the camera man closes switch I1., relay 21 willoperate, connecting power from the three-phase bus-bars 45, 50, 55through wires `44, 49, 54 to the springs of relay 21. The left-hand makespring of relay 21 connects wire 44 to wire 43, thence through wire 19to the upper terminal of the lower section of jack J3. The center makespring of relay 21 connects wire 49 through resistor 89 and wire 8| tothe second terminal of the lower section of jack J3. The right-hand makespring of relay 21 connects wire 54 through resistor 82 and wire 83 tothe third terminal of the lower section of the jack J3. The upper threeterminals of the lower section of jack J3, Fig. 5, are connected to theupper three terminals of plug 38, Fig. 4, and thence to the tappings onthe armature windings of the camera motors. Thus when the switch I1 isclosed by the camera man, operating relay 21, three-phase alternatingcurrent is applied to the motor and the motor starts. As soon as themotor attains suflicient speed, the back electromotive force generatedin one phase of the armature winding reduces the voltage loss in theresistors 89 and 82, permitting relay 84 to operate and short- Theresistors 8D and 82 and the relay S4 will thus operate to re* duce theshock on starting, in a manner similar to the operation of the resistors28 and 34 and relay- 39 when operating on direct current. The

voltage generated in the armature of the motor and appearing across thedirect current commutator causes a current to fiow through the shunt eld39 to the fourth terminal of plug 39, Fig. 4, thence to the fourthterminal of the lower section of jack J3, Fig, 5, through resistor 85,thence through the fifth terminal of the lower section of jack J3 andthe fifth terminal of plug 30, Fig. 4, back to the armature. Thiscircuit provides shunt field excitation for the motor.

In a similar manner, by closing the starting switch at the motor of thesound recorder, the relay 50, Fig. 5-A, operates, supplying threephasecurrent from the three-phase bus-bars to the recordcr motor, one phasebeing supplied through the resistors 85, 81. When the motor associatedwith the sound recorder comes up to speed, relay 88 operatesshort-circuiting the resisters 86, 81. Also by closing switch 65 andthus operating relay I9, the motors of camera No. 3

and of the sound recorder will be startedin a manner similar to thesimultaneous starting of the motors on direct current.

The voltage generated in the armature of the motor and appearing acrossthe commutator causes a current to flow through the series eld 3| of themotor, Fig. 4, lower terminal of plug 30, lower terminal of the lowersection of jack J3, Fig. 5, winding of relay 89, fifth terminal of thelower section of jack J3, fifth terminal of plug 39, Fig. 4, back to thecommutator, thus operating relay 89. The operation of relay 89 closes acircuit from the high voltage and of the left-hand winding of theauto-transformer 15 through Wire 92, lamp 9|, resistor 90, make springsof relay 89, wire 98, make springs of switch 14, wire 91 to the highvoltage end of the right-hand winding of the auto-transformer 15, thuslighting the lamp 9|. The lighting of the lamp 9I and its steady burningindicates that the corresponding motor has come up to speed and is insynchronism with the other motors in the system.

If the motor should get out of synchronism with the other motors in thesystem, there will be a sudden reversal of polarity across thecommutator which will cause the relay 89 to fall back. When the relay 89falls back, the lamp 9| individual to the motor will be momentarilyextinguished. A circuit is also closed from the high voltage end of theleft-hand winding of the autotransformer 15 through wire 92, lamp 93,resistor 94, wire 95, upper make springs of switch I8, break contacts ofrelay 89, wire 96, lower make springs of switch 14, wire 91 to the highvoltage end of the right-hand winding of the auto-transformer 15, thusmomentarily lighting the lamp 93 and indicating that one of the motorshas dropped out of synchronism. The simultaneous extinguishment of thelamp, such as lamp 9|, corresponding to the motor, indicates which oneof the motors has dropped out of synchronism. If the lamps 9| and 93continue to light intermittently, it indicates that the particular motoris overloaded and is slow in coming up to speed.

As described hereinabove, the operation of relay I9 will start themotors of camera No. 3 and of the sound recorder. Relay I9 may also beoperated by closing switch |98 thus forming a circuit from the highvoltage end of the righthand winding of the autotransformer 15, wire 98,through the springs of switch |80, wire I 83, lower break springs ofswitch 65, Wire 56, winding of relay I9, wire 81, upper break springs ofswitch 65, wire 92 to the high voltage end of the lefthand winding ofthe auto-transformer 15, thus operating the relay I9 across one phase ofthe auto-transformer 15.

All of the motors associated with a given control cabinet may be startedsimultaneously with all the motors associated with one or more controlcabinets. As shown in Fig. 1, when two cabinets are associated to form alarge system, the cabinets are interconnected by connecting the plug P5,Fig. 5-A, of one cabinet to the jack J5 of the other cabinet. Asdescribed above, the operation of switch |90 will start all the motorsassociated with a given cabinet. Let us assume that two cabinets areinterconnected together and that switch |00 of the second cabinet hasbeen closed thus starting all the motors asso ciated with that cabinet.By closing switch in the distant cabinet, power is supplied by the highvoltage end of the right-hand winding of the auto-transformer 15associated with that cabinet and flows along wires 198, switch |00, wireto the lower terminal of the jack J 5^which is interconnected with theplug lP on the rear control cabinet so that the current flows from the'lower terminal of plug P5, wire |02, |0I, wire |03 through .the lowerbreak contact of switch 65, wire 66,'wincling of relay |9, wire 61,upper break contact of switch 65, wire 92 to the high voltage end of theleft-hand winding of the auto-trans- .former in the control cabinet. Asthe autotransformers 15 in both of the cabinets are supplied with powerfrom the same three-phase power supply, current will fiow through thiscircuit and will operate relay I9 in the near control cabinet thusstarting the motors of this control cabinet simultaneously with thestarting of the motors'in the distant cabinet. The motors of any numberlof cabinets may thus be started from any one of the cabinets.

As the motor driving the sound recorder is directly connected to theinterlock bus-bar, if two cabinets were joined directly together, themotors of the two sound recorders would be directly interconnectedthrough the interlock busbar andthe synchronizing current might produceburning of the commutators. To prevent this effect, the interlockbus-bars 45, 50 and 55 are connected through the lamps |04, |05', |06and Wires |01, |08 and |99 to the three 'Lipper terminals of theinterconnecting plugs P5, Fig. 5-A. Thus when two cabinets areinterconnected the ballast lamps |04, |05 and |06 will be connected inthe interlock circuit between the two cabinets.

It is very important that each take of a motion picture productionshould be made at a known Aspeed so that the various takes willsynchronize The contactV arm of the switch I|2 is connected` Vto themid-point of a differentially wound frequency meter ||3 associated witha plurality of frequency selective, networks for determining the v Yrange of the frequencies to be measured.

In the position of the key H8, as shown, one winding of the meter ||3 isconnected through the adjusting variable resistor ||4, through inductor||5 to wire H1, and through capacitor H6 and upper break springs of `key8 to wire V|'|1. The inductor I |5 and capacitor I6 are thus linparallel relationship and form a frequency selective resonant network.The other windingr of the meter ||3 is connected through wire ||9 to theinductor |20 and capacitor |2| in` parallel, lower break springs of keyI|8 to wire I1. The inductor |20 and capacitor |2VI also form a resonantnetwork. One network resonates at a frequency slightly above the normalfrequency, the other networkV resonates at a frequency slightly belownormal frequency, and the networks are adjusted sol that at normalfrequency, the currents in thetwo windingsAY are equal and the meterisbalanced, but at any other frequency the currents are unequal and themeter is defiected from a central position. When the motors are runningVat subnormal speed the range of meter H3, may be increased by operatingkey H8, thus connecting the inductor ||5 in parallel with resistor |22to one winding of the meter, and the capacitor |23 in series withresistor |24`to the other winding of the meter. The range of frequencieswhich may begmeasured in the second case is much wider than the vrangewhich may be measured withthe two tuned circuits used in the first case.

When-the motion picture record andthe sound record are made on separatemachines, the motion picture film and the sound record must be marked atthe beginning of each take vso that the picture record and the soundrecord may be synchronized for the production of the nal combinedrecord. These synchronizing marks are commonly known as bloop marks. TheVsynchronizing circuit may be' manually operated from any one of thecontrol cabinets associated in the system. A circuit may be traced fromthe high potential end of the right-hand winding of the auto-transformer15, wire 90, switch |25, wire 99, to the lowest terminal of the plugassociated with any of the motors, such as plug P3, Fig. 5, thence tothe lower terminal of jack 25, Fig. 4, through the lamp |26 vand thebuzzer |21 to the fifth terminal of jack 25, thence to the fifthterminal of plug P3, Fig. 5, wire |28 and lamp |29 and wire 92 to thehigh potential end of the left-hand winding of the auto-transformer 15,Fig. 5-A. Thus by closing the switch |25, the lamps in the cameras fog ashort section of the picture film and the buzzer gives an audible signalto the artist that the system is ready for the take The alternatingcurrent from the auto-transformer 15 is derived from the power supplywhen the system is operated on alternating current and is derived fromthe interlock bus-bars when the system is operated on direct current. Apilot light, such as the lamp |29, is provided for each motor, the lampfor the recording motor beingshown on Fig. 5--A as lamp |30. When theswitch |25 is closed, the pilot light in the control cabinet glows dimlywhen the blooping circuit is normal, does not light at all when thebloopingA circuit is opened and glows brilliantly if the lamp in thecamera is short-circuited. The blooping signal supplied through the lamp|39 to the sound recorder may operate a lamp which fogs the film in amanner similar to the fogging of the picture nlm or this current may besupplied through the recording circuit to the recording device so thatthe sound record will show a short section of an alternating currentrecord of constant amplitude. When two or more cabinets areinterconnected, closing switch |25 completes a circuit from the highvoltage end of the right-hand winding of auto-transformer 15, wire 98,switch |25, wire 99 to fifth terminal of jack J5, thence to fifthterminal of plug P5 in all the other cabinets, and in those cabinetsfrom fth terminal of plug P5, wire 99, lower terminal of the motorplugs, such as P3, through the blooping lamp and buzzer at the camera,fifth terminal of P5, wire |28, lamp |29, wire 92 to the high voltageend of the left-hand winding of the auto-transformers 15 in the othercabinets, thus blooping the cameras and sound recorders associated withthe other cabinets.

When the recording system is to be used only in the studios, as shown inFig. 2, the control cabinet may be simplified by `the omission of thedirect current control features. An 4alternating current control cabinetof this type is shown in Figs. 6 and 6-A. Three-phase alternatingcurrent from the studio power supply is connected to the upper threeterminals of the plug P6, Fig. G-A. The

alternating current supply in the studio will normally be at one of thecommon commercial voltages, in many cases 220 volts. This 220-voltsupply is connected to the three-phase autotransformer |3| where thevoltage is stepped down to 61 or 65 volts and connected from theautotransformer |3| to the three-phase voltage select* ing switch |32.The low voltage alternating current is supplied to the alternatingcurrent busbars |33, |34, and |35. A circuit may be traced from theincoming alternating current supply bus-bar |36, wires |31 and |38 tothe second terminal of the plug P4, Fig. 6, thence to the secondterminal of jack 25, Fig. 4, through the film buckle switch 25 and theswitch |1 when closed by the camera man to the fourth terminal of jack25 thence to the fourth terminal of plug P4, Fig. 6, wire |39, left-handbreak contact of relay |40, wire |4|, winding of relay |42, wire |43,back to the studio alternating current power supply, thus -operatingrelay |42 when the switch |1 is operated. The operation of relay |42closes a circuit from the low voltage alternating current bus-bars |33,|34 and |35 through the make contacts of relayA 42, thence through theresistors |44 and |45 `to the three-phase leads |46, |41 and |48connected to the three upper terminals of the jack J4, Fig. 6, which areconnected to the upper three terminals of plug 30, Fig. 4, thence to thewinding of the camera motor. Thus yby closing the switch l1, Fig. 4, thecamera man may individually start the motor of one camera. As soon asthe motor has attained suiicient speed, the generated electromotiveforce will operate the relay |49 thus short-circuiting the resistors |44and |45.

In order to start all of the motors associated with the control cabinetfrom the control cabinet, switch |50 is operated closing ya circuit fromthe studio power supply bus-bar |36 through the upper make Contact ofswitch. |50, wire |5I,

windings of relays |40 and |52 in parallel, wire |53, t the studio powersupply bus-bar |43, thuis operating relays |40 and |52.

When the motors are to be controlled from the control cabinet, thedisconnect switches, such as |55, for each motor associated with thecabinet are closed. The operation of relay |40 closes a circuit from thestudio power supply bus-bar I 43 through the winding of the start relay|42, wire |4|, left-hand make Contact of relay |40, wire |54, lower makecon-tact of disconnect switch |55, wire |55, to the third terminal ofplug P4, Fig. 6, thence to the third terminal of jack 25, Fig. 4,through the film buckle switch 26 to the second terminal of jack 25,Fig. 4, thence to the second terminal of plug 4, 6, wire |38, wire |31,lto the studio power supply, thus operating the relay |42 and startingthe motor of the camera.

.A circuit may be traced from the studio power supply bus-bar |43through lamp |51 and resistor |58, wires |59 and |60, through the breakContact of relay IBI, wire |31 to the studio power supply, lighting lamp|51.

The winding of the relay |6| is connected to the lower two terminals ofthe jack 4, Fig. 6, thence to the lower two terminals of plug 30, Fig.4, connecting the relay across the armature and series eld of the motor.As the motor comes up to speed, the electromotive force generated in thearmature will eventually become large enough to operate the relay IGI.The operation of relay |6| closes a circuit from the studio power supplybus-bar |43, through lamp |02, resistor |03, wire |64, make contact ofrelay ISI, to the studio power supply bus-bar |31, thus lighting thelamp |62 individual to this particular motor. Thus, as each motorassociated with the cabinet comes up to normalspeed, a lamp, such aslamp |52, lights indicating `to the operator of the cabinet that thatyparticular motor has come up to speed. As soon as all of the motorsassociated with a particular cabinet have attained normal speed, thusoperating all of the relays similar to relay I6 I, the lamp |51 will beextinguished.

If any of the motors should get out of synohronism with the supply line,there will be a sudden reversal of polarity across the armature andseries eld of that motor, thus releasing the relay |'B|, associate-dwith the motor, momentarily extinguishing the lamp |62 associated withthe motor, and lighting the lamp |51, common to all the motors. As soonas the armature of the motor has slipped back, an angle equivalent toone polepiece, the motor will again be in synchronism with the othermotors, the relay |6| will operate extinguishing the lamp |51 andlighting the lamp |62. If, however. any particular motor is overloaded,or otherwise defective, so that it cannot attain synchronism with theother motors, the alternate hashing of the lamps |51 and |62 warns theoperator of the control cabinet that the particular motor indicated isunable to attain syn-chronism with the other motors. The operator canthen take such steps as are necessary to clear the trouble.

A start relay |42, a slow-start relay |49, and a synchronism indicatingrelay |6| are provided for each motor associated with the controlcabinet, while a switching relay |40 is provided for each two motorsassociated with the cabinet. In the studios, the sound recordingmachines may be permanently installed in a recording room, thus thecontrol cabinet is adapted to control four cameras only. If portablerecorders are also used in the system, the cabinet shown in Fig. 5 maybe used.

After all of the motors have been started and brought up to speed inproper synchronism, the switch |65 is operated, closing a circuit fromthe studio power supply bus-bar |36 through meter |66, switch |65, wire|61 to the blooping busbar |68 which connects to the lowest terminal ofthe plug, such as plug P4, Fig. 6, associated with each camera. Thecircuit extends from the low-v est terminal of plug P4, Fig. 6, to thelowest terminal of jack 25. Fig. 4, thence through the "bloop light |26and buzzer |21 to the fth. terminal of jack 25, Fig. 4, thence to thefth terminal of plug P4, Fig. 6, wire |69, upper make contact of thedisconnect switch |55, lamp |10, to the studio power supply bus-bar |43,thus bloop ing each camera by exposing a short length of the film in thecamera, and also giving an audible signal to the personnel on the setthat the camera is now in condition to lm the action. This circuit alsolights an individual lamp |10 for each motor at the control cabinet, andgives an indica tion on the meter |66, common to all the camerasassociated with a given cabinet. If the lamp |10 fails to light, itindicates that the circuit to that particular camera is open; if thelamp |10 only gives a dim light, it indicates that the circuit to thatparticular camera is functioning properly; and if the lamp |10 lightswith unusual brilliancy, it indicates that the circuit to thatparticular camera has become short-circuited at some point. Thus theoperator at the control cabinet can check whether all of the camerashave been successfully blooped Two or more cabinets of this type may beinterconnected together andthe combined system may be controlled fromany one of the cabinets. To interconnect two cabinets of this type, thejack J5, Fig. -A, of one of the cabinets is connected to the plug P ofthe other cabinet. chronizing current can then circulate from thethree-phase bus-bars |33, |34, |65 of the irst cabinet through the upperthree terminals of the jack J5, to the upper three terminals of the plugP5 of the second cabinet, thence through the ballast lamps 11|, |12, |13in the second cabinet to the three-phase bus-bars |33, |34, in thesecond cabinet. When the motors of the two cabinets are in synchronismor approximately so, the synchronizing currents are small, theresistance of the lamps |1|, |12, |13 is practically the cold resistanceof the lamp and therefore comparatively small so that the resistanceinserted between the two groups of motors is small. However, if onegroup of motors is out of synchronism with the other group,comparatively large synchronizing `current tends to flow between the twogroups of motors, but this current flowing in the lamps |1|, |12, |13will increase the resistance of the lamps to a Value approaching the hotresistance of the filament and this increase in resistance will limitthe synchronizing current to a value which will not adversely aiect themotors associated with either cabinet.

To start the motors associated with all of the cabinets interconnectedto form a system., the switch in one of the cabinets is closed. Thiscompletes a circuit from the studio power supply bus-.bar |35 throughswitch |58, wire 15|, wire |14 to the lowest terminal of the jack J 5,thence to the lowest terminal of the plug P5, or jack J5, of the othercabinets and thence through the wire |14, wire |5|, relays |40 and |52in parallel, wire |53, wire |43, to the studio power supply =bus bar |43in the other cabinets, thus operating the switching relays 46 and |52and starting the motors of the different cabinets.

When two cabinets are interconnected, a circuit may be traced from thestudio power supply bus-bar |43 in one oi the cabinets through the lamp|51, resistor |58, wire |59, wire |68 to the fourth terminal of jack J5,thence to the fourth terminal of plug P5, or jack J5, in the othercabinet, thence over wire |68, break Contact of relay |6| to the studiopower supply bus-bar |31, thus lighting the lamp |51 in all of thecabinets. As each motor associated in the system comes up to speed, thecorresponding relay |6| operates. When all of the relays I5! associatedwith all of the motors in the system have operated, the lamp |51 in allof the cabinets Will be extinguished. Thus an operator at any one of thecabinets can tell when all of the motors associated in the system havecome up to speed. If any of the motors associated in the system shoulddrop out of synchronism, the corresponding relay |6| will be releasedlighting all of the lamps |51 in the various cabinets and extinguishingthe running lamp |52 individual to that particular motor. A continuedflashing of the lamp |51 thus indicates that some one, or more, of themotors have not attained synchronism.

After all of the motors associated in the system are running insynchro-mism at normal speed, the switch |55 in any one of the cabinetsmay be closed. This completes a circuit from the studio power supplybus-bar |36 through the meter |66, and switch |55, wire |51, wire |68 tothe fth terminal of ljaclr J5, thence -to the fth terminal of plug P5,or jack J5, in the other cabinet, thence Synin those cabinets over wire|58 to the sixth terminal of the plug P4, thence to the jack 25, Fig. 4,through the bloop light and buzzer associated with that camera to thefifth terminal of jack 25, thence in that cabinet from the fifthterminal of plug P4, wire |59, upper make contact of disconnect switch|55, lamp |18 to the studio power supply bus-bar |43, thus blooping allof the cameras associated with all of the other cabinets, and lightingthe b1oopng" lamps associated with those cameras in the distant cabinetand indicating on the meter |66 of the controlling cabinet that theother cabinets have been successfully blooped The alternating currentcontrol cabinet shown in Figs. 6 and -A may be associated with thealternating current, direct current cabinet shown in Figs. 5 and 5-A,when the latter is operated on alternating current. In this case thejack J5, Fig. 6-A, is interconnected with the yplug P5, Fig. 5-A. As thestarting, synchronizing and blooping of this combination issubstantially the same as the starting, synchronizing and blooping oftwo cabinets of the type shown in Figs. 6 and 6--A, a detaileddescription of the interconnection between the alternating currentcabinet and the alternating current, direct current cabinet is believedto be unnecessary.

The alternating current control cabinet shown in Figs. 6 and 6--A, maybe associated with a sound recording control cabinet shown in Fig. '1.The plug P6, Fig. 6A, is connected to the jack |15 in Fig. 7, thedisconnect switch |16 is closed and the power supply switch |11 is alsoclosed. For slating or individually starting the recorder motor at therecorder, the switch |18 is operated, thus closing a circuit from one ofthe power supply bus-bars through the upper make contact of the switch|18 and the starting relay |19 to another of the power supply bus-bars,thus operating relay |19. The operation of relay |19 connects the powersupply bus-bars through the resistors and |8| to the wires |82, |83,|84, leading to the recorder motor and starts the recorder motor. Assoon as the recorder motor has attained suiiicient speed, the generatedelectromotive force operates the relay |85, shortcircuiting theresistors |80 and |8|. The operation of relay |19 completes a circuitfrom the upper power supply bus-bar through the break springs yof relay|85, resistor |86, lamp |81 and wire |88 to the lower bus-bar of thepower supply, thus lighting the lamp |81. The operation of relayconnects the upper bus-bar of the power supply through the make springsof relay |85, resistor |89, lamp |98 to wire |88 running to the lowerbus-bar of the power supply, thus lighting the lamp |96 andextinguishing the lamp |81.

After the recorder motor has come up to speed, as shown by the lightingof the lamp |90 and the extinguishment of the lamp |81, the switch |94is closed completing a circuit from the upper power supply bus-barthrough wires |9| and |92, through the meter |83, switch |94, to thelower make contacts of switch |16, wire IQE, through the primary windingof the transformer |96, resistor |91 and wire |63 to the lower powersupply bus-bar, thus applying alternating current to the primary windingoi the transformer |96. The secondary winding of the transformer |96 maybe connected to the sound recording circuit leading to the soundrecording device, so that the operation of the switch |94 will cause thesound recording device to produce .a short length of record of theconstant frequency, constant amplitude current supply from lthe powerbus-bar, or this winding may be connected to a small lamp so placed inthe recorder that it will expose a short length of the sound record, orthe current from this transformer may operate any other electricaldevice that will a distinctive mark upon the sound record. The operationof key |94 thus bloops or makes a starting mark on the sound record.

With the switch |18 in the unoperated position, the motor may also bestarted by the operation of switch |99 which completes a circuit fromthe upper bus-bar of the power supply through wires |9| and I 92 throughswitch |99, upper make contact of switch |16, lower make contact ofswitch |18, through the winding of the starting relay |19 to the lowerbus-bar of the power supply, thus operating the relay |19 and startingthe motor.

When the recorder control cabinet shown in Fig. 7 is interconnected withone or more of the alternating current control cabinets shown in Figs- 6and 6-A, power is supplied through switch |11 to the three upperterminals of jack |15, thence to the bus-bars in the other controlcabinets. The operation of switch |99, Fig. 7 completes a circuit fromthe upper power supply bus-bar through wires |9|, |92, switch |99, wire209, to the lowest terminal of jack |15, thence to the lowest terminalof plug P6, Fig. 6-A, wire |14, windings of relays |40 and |54, wires|53 and |43, to the top terminal of plug P6, thence to jack |15, Fig. 7,wire |98 to the lowest bus-bar of the power supply, thus operatingrelays |40 and |52, Fig 6-A. and starting the motors of the cameras. Acircuit may also be traced through the upper power supply bus-bar, Fig.7, wire |9|, to the third terminal of jack |15, thence to the thirdterminal of plug P6, Fig. B-A, Wire |36, L,

make springs of switch |50, when operated, wires I5! and |14, lowerterminals of plug P6 and of jack |15, Fig. 7, wire 200, upper makesprings of switch |16, lower break springs of switch |18, winding ofrelay |19 to the lower power supply busbar. Thus the operation of switch|50 in the alternating current control cabinet Fig. 6-A, will start themotor associated with the sound recorder. Thus when one or more of therecorder control circuits are associated with one or more of thealternating control cabinets, each of the motors in the system may beindividually slated or started at the motor and all of the motorsassociated in the system may be started from any one of the cabinets orfrom any of the recorder control circuits.

When the start relay |19, Fig. 7, operates, it completes a circuit fromthe upper power supply bus-bar through the upper make springs of relay|19, the break springs of relay |85, wire 20|, to the fourth terminal ofjack |15, thence to the fourth terminal of plug P6, Fig. 6A, wire |60,wire |59, resistor |58, lamp |51, wire |43, to the upper terminal ofplug P6, thence to the upper terminal of jack |15, Fig. 1, wire |98 tothe lower bus-bar of the power supply, thus lighting the lamp |51, Fig.6-A, and holding the lamp lighted until the relay |85 has operated. Acircuit may also be traced from the lower power supply bus-bar, Fig. 7,wire |88, lamp |81, resistor |86, wire 20| t'o the fourth terminal ofjack |15, thence to the fourth terminal of plug P6, Fig. G-A, wire |60,contacts of relay |6I, wire |31, to the third contacts of plug P6,thence to the third contact of jack |15, n

Fig, 7, wire |9| to the upper power supply busbar, thus lighting thelamp |81. In other words, when any motor in the system is started, thelamps |81, Fig. 7 and |51, Fig. 6-A, are lighted and remain lighteduntil all of the motor associated in the system have been started andhave come up to normal speed. Also, if any motor should drop out ofsynchronism thus releasing the corresponding relay |85, Fig. 7. or relay|6|, Fig. 6, the lamps |51, Fig. 6, and |81, Fig. 7 will both light,showing that some motor in the system is not properly synchronized.

When the sound recorder is blooped by the operation of switch |94, acircuit is closed from the upper power supply bus-bar, wires |9| and|92, meter |93, switch |94, wire 202, to the fifth terminal of jack |15,thence to the fth terminal of plug P5, Fig. 6-A, to the blooping"bus-bar |68, thence through terminal 6 of any of the camera plugs toterminal 6 of jack 25, Fig. 4, through the blooping light |26 and buzzer|21 to the fth terminal of jack 25, thence to the fth terminal of thecamera plug, Fig. 6, wire |69, upper make contact of the disconnectswitch |55, lamp |10, wire |43, upper terminal of plug P6, upperterminal of jack |15, Fig. 7, wire |98, to the lower power supplybus-bar, thus blooping all of the cameras when the switch |94 isoperated to bloop the recorder. A circuit may also be traced from theupper power supply bus-bar, Fig. 7, third contact of jack |15, to thirdcontact of plug P6, Fig. 6-A, wire |36, meter |66, switch |65, wire |61,fth terminal of plug P6, and of jack |15, Fig. 7, wire 202, lower makesprings of switch |16, wire |95, primary winding of transformer |96,resistor |91, wire |98, to the lower power supply bus-bar. Thus theoperation of switch |65, Fig. 6A, will bloop all of the cameras and willalso bloop all of the recorders.

In some cases an oiiicial, such as the director or his assistant, maydesire to control the operation of the system from some vantage point onor near the set. An extension control box as shown in Fig. 8 may beprovided for this purpose. In Fig. G-A, a circuit may be traced from theupper terminal of jack J6, wire |43, lamp |51, resistor |58, wires |59and |60, to the third terminal of jack J 6. The plug 205, Fig. 8,connects to the jack J6, Fig, 6--A, and it will be noted that the lamp203 and resistor 204 are connected between the rst and third terminalsof the jack 205, thus connecting the lamp 203 in parallel with the lamp|51 on Fig. 6--A. The lamp 203 will thus indicate the starting andsynchronizing of the motors in the same manner as the lamp |51, Fig.6-A.

In Fig. 6--A, a circuit may be traced from the second terminal of thejack J6, wire |36, switch |50, wire |5|, wire |14, to the fifth terminalof jack J6. Similarly in Fig. 8, a circuit may be traced from the secondterminal of plug 205, switch 206 to the iifth terminal of plug 205. Thusthe switch 206 in Fig. 8 is in parallel with the starting switch |50 inFig. 6-A, and the operation of switch 206, Fig. 8, will start all of themotors associated in the system.

In Fig. 6-A, a circuit may be traced from the second terminal of thejack J6, wire |36, meter |66, switch |65, wire |61, to the fifthterminal of the jack J6. Similarly, in Fig. 8 a circuit may be tracedfrom the second terminal of plug 205, through meter 201 and switch 208to the fourth terminal of the plug 205, thus placing the combination ofthe meter 201 and switch 208 42-I5, wire 2315, Vstarting the recordermotor. Y Fig. 4 it will be noted `that the second and third in parallelwith the combination of the blooping meter HB6 and switch I51. Theoperation of switch 203, Fig. 3, will thus bloop all ofthe cameras andrecorders associated in the system.`

The meter 203 is in series in the bloop circuit and acts as a pilotdevice to indicate whether the bloop circuit is normal. The meter 298has no meter scale, but is equipped with a pointer, or other indicator,which may be manually adjusted. The bloop circuit is checked before use,and the pointer set at the correct value for the lamps in use,thereafter, when the circuit is blooped, the meter hand should move tothe pointer. If the meter does not read the correct value, it indicatesthat one camera has not been properly blooped so the take is stoppeduntil the trouble is rectified.

When operating on location, away from commercial power supplies, orunder any other condition, in which operation on batteries is consideredto be desirable, the combined alternating current, direct currentcontrol cabinet shown in Fig. 5 maybe simplified by the omission of thealternating current feature, to form a direct current control cabinet asshown'i'n Figs. 9 and 9 2.. The operation of the direct currentcontrolcabinet shown in Figs. 9 and 9-A is Very similar to the operationof the combined control cabinet shown in Fig. 5 when the combinedcabinet is operated on direct current. A tapped battery or other sourceof direct current isconnected to the plug P9, Fig. 9-A, the positiveterminal of the battery being connected to the upper terminal of theplug and the negative terminal of the battery to the lowest terminal ofthe plug. The switch 299 connects the desired tap of the battery to thepositive bus-bar 2I9. The voltmeter 2I-2 measures the voltage appliedbetween the positive bus-bar 2W and the negativerbus-bar 2 I I. Thedisconnect switches, such as switches 2I3 and 2I4, associated with allof the motors which are to be operated in the system, are closed. Thedisconnect switches 2I5, 2 I6 and'2 I1 are also closed. As shown on Fig.4, by operating the switch I1 the camera man completes a circuit fromthe second terminal of jack 25 Vthrough the film buckle switch 26 andswitch I1 to the fourth terminal .of jackV 25. The jack 25 is associatedwith one of the plugs PI toV P4, Fig. 9. Thus, considering the plug P3,Fig. 9, a circuit is completed from the negative bus-bar 2II through thesecond terminal of plug P3 to the fourth terminal of plug P3, wire 2I9,left-hand break terminal of relay 2 I 9, wire 229, switch 2 I 9, wire 22I, winding of start relay 222, wire 223, to the positive terminal of thebattery, thus operatingthe start relay 222 and connecting the batterybus-bars 2li! and 2II, through the make contacts of relay 222, andresistors 224 and 225 to the cameray motor, Fig. 4, thus starting themotor. When the motor comes up to speed, the generated electromotiveforce causes the operation ofrelay 226 thus short-circuiting theresistors 224 and225. Similarly, the operation of the starting switch atthe recorder motor completes a circuit between the rsecond and fourthterminals of Vthejplug P4, operating the relays 221 uand 22S through theswitch 2I1, the righthand break contact of relay 2 I9, wire 235, switchIn terminals of the jack 25 are connected through the film buckle switch28. -By the operation of switch 230, Fig. 9-A, circuit is completed fromthe positive bus-bar 2 I9 through the upper makey springs of switch 230,wire 23|, windings of the switching relays 2I9, wire 232, lower makeContact of .switch 239-, resistorV 229, to the negative bus-bar 2II,thus operating the switching relays l2I9. The operation of the switchingrelay 2 IS completes a circuit from negative bus-bar 2II, through thesecond terminal oi the plug P3, through the film buckle switch, Fig. 4,the third terminal of plug P3, wire 2,33, make con"- tact of relay 2I9,wire 229, switch ZIS, wire 22I and winding of start relay I222, to thepositive terminal of the battery, thus operating the start relay 222 andstarting the motor of camera No, 3. A similar circuit may be traced fromthe negative bus-bar 2II through the second contacts of plug P4, to thethird contacts of plug P4. wire 234, right-hand make contact of relay2I9, wire 235, switch 2I5, wire 236, winding of relay- 221 to thepositive bus-bar, thus operating the start relay 221 and starting themotor associated with the sound recorder. The synchronizing tappings onthe armature of the motor of camera No. 3 are connected through theballast lamps 231, 238, 239 and the three lower springs of thedisconnect switch 2 I4 with the synchronizing busbars. The synchronizingtappings on the armature of the recorder motor are similarly connectedthrough the jack J4, and the three lower springs of the disconnectswitch 2I3 with the synchronizing bus-bars. Current is supplied to theshunt neld of the motor of camera No. 3 through the iield rheostat 240and to the shunt iield oi the recorder motor through the field rheostat24|.

The operation of the start relay 222 completes a circuit from thepositive bus-,bar 2'I0 through the lamp 242, resistor 243, wire 244,resistor 225,

left make contact of the start relay 222, to the negative bus-bar 2I`I,thus lighting the rlamp 242, indicating that the motor of camera No. 3is running at normal speed. An intermittent flashing of the lamp 242will indicate when the motor of camera No. 3 is out of synchronism.Similar lamps and resistors, such as lamp 245 and resistor 246, areprovided for the other motors associated with the cabinet.

The three-phase transformer 241 is energized by the synchronizingcurrent flowing in the interlock bus-bars. The operation of switch 248,Fig. 9-A, completes a circuit from the righthand winding of thetransformer 241, through the switch 249, wire 249, resistor 252, primarywinding of transformer 25I, wire 252, lamp 253, disconnect switch 2I3,wire 254, back to the lefthand winding of the transformer 241, thussupplying alternating current of constant frequency and constantamplitude to the primary of the transformer 25I. The secondary windingof the transformerv 254 is connected through the two lower terminals ofthe plug P4, to the sound moorden-thus supplyingY current either tothesound recording device, or to some other device that will make astarting -mark on the sound record. The operation `of the switch 248also f completes Va circuit from the right-hand winding ofthetransformer v241,-switch 24B, wire 249, wire 255, to the lowest terminalof the plug P3, Fig. 9, thence to the lowenterminal of the jack 25, Fig.4, through the lamp |26 and the buzzer |21 to the fifth terminal of thejack-25, thence to the fth terminal of the plug P3, Fig. 9., wire 256and lamp 251, disconnect switch 2I4, wire 254, to the lefthhand windingof the transformer '241, thus lighting the lampfIZG inthe camera tocause a short exposure of the nlm in the camera and also operating thebuzzer |21 to notfy the personnel on the set that the camera is readyfor the take. The operation of the switch 248 also causes the lamp, suchas lamp 253 and lamp 251, individual to each of the motors, to light,thus indicating that that camera or recorder has been successfullyblooped.

One phase of the interlock bus-bars individual to each motor and of theinterlock bus-bars common to all the motors is wired to the switch 258.The meter 259 and network 260 associated with the switch 258 thus canmeasure the frequency of the interlock current from each of the motorsand this frequency is an indicator of the speed oi the motor.

As shown in Fig. 3, two or more of the direct current control cabinets,shown in Figs. 9 and 9-A, may be interconnected together or they may beinterconnected with one or more of the alternating current, directcurrent control cabinets, shown in Fig. 5, when the latter cabinets areoperated o-n direct current. To interconnect two cabinets, the jack J5,SA, is connected to the plug P5 of the second cabinet. The interlockbus-bars of the iirst cabinet which are connected to the three upperterminals of the jack J5, are thus connected to the three upper terminals of the plug P5 in the second cabinet, thence through wires 254,262, 263 and the ballast lamps 254, 255, 2'56 to the common interlockbus-bars of the second cabinet. The operation of switch 261 in the firstcabinet completes a circuit from the right-hand winding of transformer241, switchf261, wire 258, to the lowest terminal of the jack J5, thenceto the lowest s' terminal of the plug P5, in the second cabinet, wire259, upper break contact of switch 235i, wire 23|, winding of switchingrelays, such as relay 2 i9, Fig. 9, wire 232, lower break springs ofswitch 23E, wire 254 to the left-hand winding of the transformer 2:3? inthe second cabinet. As all of the transformers, such as transformer 241,in the various cabinets are supplied with power from the commoninterlock bus-bars between the two cabinets, the closing oi switch 251in the first cabinet will operate the switching relays in the secondcabinet and start all the motors associated with the second cabinet.Also, il the switch 235 in the iirst cabinet is unoperated, the closingof the switch 251 in the first cabinet will also operate the switchingrelays such as relay k2li), Fig. 9, and start all the motors associatedwith the first cabinet. Thus the operation of the switch 261 in any ofthe cabinets associated together to form the system will start all ofthe motors associated in the system.

As described hereinabove, the operation oi switch 248 will bloop all thecameras and recordel-s associated with the control cabinet. Theoperation of the switch 248 in one o the cabinets will also complete acircuit from the righthand winding of the transformer 2M in that cabinetthrough switch 248, wire 249, wire 255, to the fifth terminal of thejack J5, thence to the fifth terminal oi the plug P5 in the secondcabinet and in that cabinet over wire 255 and the corresponding cameraplug to the blooping lamp and buzzer in the camera, wire Fig. 9, lamp251, disconnect switch 2M, wire 254, to the left-hand winding of thetransformer 241 in the second cabinet, thus blooping all ol the canierasassociated with the second cabinet simultaneously with the blooping oithe cameras associated with the nrst cabinet. The operation -of theswitch 248 in the rst cabinet also closes ohms, divided as desired amongthe motors.

a circuit from the right-hand winding of transformer 241, switch 248,wire 249, wire iifth terminal of jack J5, thence to the iifth terminalof the plug P5 in the second cabinet and in that cabinet wire 255,resistor 25B, primary winding of transformer 25l, wire 252, lamp 253,disconnect switch 213, wire 254, to the left-hand winding of thetransformer`241 in the second cabinet, thus blooping the sound recorderassociated with the second cabinet.

In some cases when on location a camera be located so far away from thecontrol cabinet that the resistance of the supply lead from the cabinetto the motor becomes high enough to cause unstable operation of themotor.

With a sound recorder located near the control cabinet, a cameraequipped with the preferred iorin or" inotoiwill wor: satisfactorilywith a resistance of about eight ohms per leg, that about two thousandfeet of sixteen Brown and Sharpe copper Two cameras will worksatisfactorily with four ohms per leg, and three cameras with aboutthree ohms per leg, in other words, the total resistance may be abouteight In some cases, the locations of the cameras are such that thetot-al resistance exceeds these preferred limits.

In such cases an extension box, as shown in Fig. i0, may be insertedbetween the camera and the control box in the vicinity ci the camera. Insuch cases, the plug P3, Fig. 9, is connected to the jack 2li, Fig. l0,thence directly to the plug 212, Fig. l0, and from there to the jack 25,Fig. 4, on the camera. As the control devices associated with jack 25,Fig. fi, all operate on moderately small current, the resistance of thesignal wires between the camera the control cabinet does not preventsatisfactory operation of the control and signaling devices.

The jack J3, Fig. 9, is connected to the plug 213, Fig. 10, and the jack2'54, Fig. l0, is connected to the plug 38, Fig. 4. When the start relay222, Fig. 9, corresponding to this camera, is operated, current issupplied from the battery bus-bars in the control cabinet through thecontacts of relay 222 to the two lowest terminals of jack J3, thence tothe two lowest terminals of plug 213 through the upper contacts ofswitch 215 to the winding of relay 215, thus operating relay 215. Thetwo left-hand springs of the relay 216 connect the interlock ous-bars inthe control cabinet through the three upper terminals of plug 213 to thethree upper terminals of jack 214, thence to the three upper terminalsof plug 30, Fig. 4, to the tappings on the armature winding of thecamera motor, The two right-hand springs of the relay 215 connect alocal source of current, such as the battery 211, to the two lowestterminals of the jack 214, thence to the two lowest terminals oi plug33, Fig. ll, to the armature and iield winding of the camera motor, thusstarting the camera motor. The shunt iield resistor 218, Fig. l0, isconnected into the circuit in the usual manner. By moving the switch 215to the lower contacts, the camera man may operate the relay 216 to startthe motor when slating his camera.

What is claimed is:

l. In combination, a plurality of motors, switches individual to eachmotor located adjacent to the motor, a source of power, a controlcabinet for supplying power from said source to all of said motors, aplurality7 of two-position switches in said cabinet, connections fromthe

